In turbomachinery it is usually necessary to attach turbine disks to a turbine shaft for either having the shaft drive the disk or the disk drive the shaft. Composite disks offer better results in some operations but are more sensitive to stress risers than metallic disks. Thus, it is sometimes necessary to secure a backup disk, having the required strength, to the shaft and provide some means for locking the composite disk to the backup disk.
Bolts have been used for locking the backup disk to the composite disk but the bolt holes in the composite disk are stress raisers which can eventually lead to failure of the composite disk. Other methods of attaching the backup disc to the composite turbine disk have other problems.